Just press Windows+R and type in %APPDATA% then in the folder that opens go into Apple Computer\iTunes\iPod Software Updates and your 3.0 ipsw should be right there (Provided you downloaded it legally in iTunes).

Its not rude, it shows how bad our jailbreaking community has become from a group of people who used to push out apps, themes, tweaks and mods to people who come here and cant even use the search feature on there OS.